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Control Training and Service Manual
3 Stage Electric Reheat – With Dead Band
Temp Set Point: 70°F
Proportional Band: 8°F
Dead Band: 2°F
65 66 67 68 69 70
Decreasin
g
Temperature
Temp Set Point - (1/2 Dead Band + 1/2 Proportional Band)
DB
Reheat 1 On
Reheat 3 On
Reheat 2 On
Reheat
3 Off
Reheat
2 Off
Reheat
1 Off
Note: in the above example that the control band begins at the 70°F temperature
set point and has a length of 5°F, which is ½ of the programmed temperature dead
band value plus ½ of the programmed temperature proportional band value.
As the return air temperature decreases Reheat 1 is activated at 67.7°F or ½ of
the dead band value plus 33% of the heating control band. If the return air
temperature continues to decrease Reheat 2 will activate at 66.4°F or ½ of the
dead band value plus 66% of the heating control band. If the return air
temperature continues to decrease Reheat 3 will activate at 65°F or ½ of the dead
band value plus 100% of the heating control band.
When the return air temperature starts to increase, Reheat 3 is deactivated at
66.4°F or ½ of the dead band value plus 66% of the heating control band. Reheat
2 is deactivated at 67.7°F or ½ of the dead band value plus 33% of the heating
control band. Reheat 1 is deactivated at 69°F or ½ of the dead band value plus
0% of the heating control band.
Remember the temperature dead band value is used by the control to shift the
cooling on/ off operations away from the temperature set point.
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